The present invention relates to a magnetic tape recorder and, more particularly, to a system for controlling the running speed of a magnetic tape in a fast feed mode operation of the tape recorder.
In a prior art magnetic tape recorder, a fast feed mode operation is effected by applying a predetermined voltage to a motor adapted to drive a take-up reel while pressing a piece of felt or the like against a supply reel to develop a back tension. This is to cause the tape to move at a speed simply dependent on the friction of a tape drive system of the tape recorder and the running speed of the tape per se is not controlled.
For tapes having relatively small frictional loads, the prior art tape recorder is designed to maintain the rotation torque of the take-up reel relatively small in order that the take-up speed may be prevented from being increased or that the tape may be prevented from spilling from the supply reel at the end of a take-up operation. This, however, would consume a disproportionate period of time for taking up the tape and make the tape recorder awkward.
Meanwhile, the running speed of a tape generally depends on a frictional coefficient particular to a tape as well as on a varying tape roll radius built up on a take-up reel (referred to simply as "tape radius" hereinafter for convenience). In this situation, various malfunctions tend to result due to the absence of particular controls over the tape speed. For example, on the tape recorder with an automatic program locating system, even a "tacet" in a single musical piece might be erroneously detected as an interval between different musical pieces.